Do Children Perceive Postural Constraints When Estimating Reach or Action Planning?

Estimation of whether an object is reachable from a specific body position constitutes an important aspect in effective motor planning. Researchers who estimate reachability by way of motor imagery with adults consistently report the tendency to overestimate, with some evidence of a postural effect (postural stability hypothesis). This idea suggests that perceived reaching limits depend on an individual's perceived postural constraints. Based on previous work with adults, the authors expected a significant postural effect with the Reach 2 condition, as evidenced by reduced overestimation. Furthermore, the authors hypothesized that the postural effect would be greater in younger children. They then tested these propositions among children aged 7, 9, and 11 years by asking them to estimate reach while seated (Reach 1) and in the more demanding posture of standing on 1 foot and leaning forward (Reach 2). Results indicated no age or condition difference, therefore providing no support for a postural effect. When the authors compared these data to a published report of adults, a developmental difference emerged. That is, adults recognize the perceived postural constraint of the standing position resulting in under- rather than overestimation, as displayed in the seated condition. Although preliminary, these observations suggest that estimates of reach (action planning) continue to be refined between late childhood and young adulthood.     

On the Role of Vertical Texture Cues in Height Perception

When people judge height from the top looking down they tend to overestimate vertical distance. Initial findings suggest that this perceptual bias may be in part due to the experienced fear of falling. However, previous studies did not control for potentially relevant optical invariants, especially vertical texture gradient cues, that may inform such perceptual judgments. In this study, we examined to what degree texture gradient cues may account for the perceptual bias in height perception. To this end, in 2 different conditions in which vertical texture gradient cues were either present or absent, participants provided distance and size judgments from an elevated position (5.68 m) and from the ground. Results revealed a systematic overestimation of vertical extent and object size when judged from a height. Yet, the absence or presence of texture gradient cues did not differentially influence these judgments. Finally, although fear levels were reported to be larger at the elevated position than on the ground, fear levels did not correlate with the perceptual bias, thereby demanding further research into the mechanisms underlying the perceptual bias in height perception.     

Navigating through apertures: perceptual judgements and actions of children with Developmental Coordination Disorder

Passing through a narrow gap/aperture involves a perceptual judgement regarding the size of the gap and an action to pass through. Children with DCD are known to have difficulties with perceptual judgements in near space but whether this extends to far space is unknown. Furthermore, in a recent study it was found that adults with DCD do not scale movements when walking through an aperture in the same way as their peers. The current study, therefore, considered perceptual judgements and motor behaviour of children with DCD while looking at or walking through apertures. Twenty‐nine children with DCD and 29 typically developing (TD) children took part. In Experiment 1, participants completed a perceptual task, where they made passability judgements. Children with DCD showed a significantly smaller critical ratio (aperture size at which a participant first rotates the shoulders to pass through) compared to their TD peers. In Experiment 2, participants completed an action task where they walked through the same apertures. Children with DCD showed a significantly larger critical ratio than TD peers when body size alone was accounted for. Taken together these results suggest that perception within a static context is different from that within a dynamic context for children with DCD. However, despite this difference we have demonstrated a clear relationship between perception and action in children with DCD. A video abstract of this article can be viewed at: https://youtu.be/SABXFrAJtF8     

Throwing in the dark: improved prediction of action outcomes following motor training without vision of the action

Traditional models of action understanding emphasise the idea that long-term exposure to a wide array of visual patterns of particular actions allows for effective action anticipation or prediction. More recently, a greater emphasis has been placed on the motor system’s role in the perceptual understanding and prediction of action outcomes. There have been attempts to isolate the contributions of visual and motor experience in action prediction, but to date, these studies have relied on comparisons of motor-visual experience to visual-only (observational) experience. We conducted a learning study, where visual experience was directly manipulated during practice. Novice participants practised throwing darts to 3 specific areas of a dartboard. A group trained without vision of their action, only feedback about the final landing position, significantly improved in their ability to predict the landing position of a thrown dart, from temporally occluded video clips. The performance of this ‘no-vision’ group did not differ from a Full-vision group and was significantly more accurate than an observation-only and a no-practice control group (with the latter two groups not improving pre- to post-practice). These results suggest that motor experience specifically modulates the perceptual prediction of action outcomes. This is thought to occur through simulative mechanisms, whereby observed actions are mapped onto the observer’s own motor representations.     

The effects of perceptual similarity and category membership on early word-referent identification

We investigated the impact of perceptual and categorical relatedness between a target and a distracter object on early referent identification in infants and adults. In an intermodal preferential looking (IPL) task, participants looked at a target object paired with a distracter object that could be perceptually similar or dissimilar and drawn from the same or different global category. The proportion of target looking measures revealed that infants and adults were sensitive to the interplay between category membership and perceptual similarity. Online latency measures demonstrated an advantage for perceptually dissimilar items regardless of their categorical status, indicating that different IPL measures index different processes during target identification. Results suggest that perceptual similarity and category membership of the objects lead to competition effects in word recognition and referent identification in both adults and infants and that lexical categorization and nonlinguistic categorization processes are closely related during infancy.     

When do children begin to understand logical inference as a source of knowledge?

Previous research (Sodian & Wimmer, 1987) suggests that it is not until about 6 years of age that children come to recognize that one can gain knowledge through inferential rather than direct means. However, a great deal of research suggests that children have a sophisticated understanding of other aspects of knowledge, such as perception and communication around age 4. Three experiments were carried out in which we made important task information more salient in order to determine whether children's performance in previous research on their understanding of inference had underestimated their abilities. The design included controls to ensure that children's attribution of knowledge to the story character could not be based on an egocentric tendency to attribute their own knowledge. Results indicated that (a) enhancing the salience of important information significantly improved children's performance; (b) by 4 or 5 years of age children begin to understand inference as a source of knowledge, around the same time they evidence an understanding of knowledge gained through perception and communication; and (c) that their performance lagged slightly behind that exhibited on a standard false-belief task.     

36‐month‐olds conceal visual and auditory information from others

By three years of age, children are skilled at assessing under which circumstances others can see things. However, nothing is known about whether they can use this knowledge to guide their own deceptive behaviour. Here we investigated 3‐year‐olds’ ability to strategically inhibit or conceal forbidden actions that a nearby adult experimenter could see or hear. In the first experiment, children were more likely to disobey the adult when she did not have visual access to their activities than they were when she was looking at them. In the second experiment, in which the adult could never see the child, children refrained from making noise when engaging in a prohibited action that the adult might hear. These results suggest that by three years of age children use their knowledge of others’ perceptual states to decide whether it is safe to commit a transgression and, moreover, actively conceal perceptual cues that could reveal to others their ongoing transgression.     

Perceptually Equivalent Judgments Made Visually and via Haptic Sensory-Substitution Devices

ABSTRACT

According to the ecological theory of perception–action, perception is primarily of affordances, which are directly perceivable opportunities for behavior. The current study evaluated participants’ ability to use vision and haptic sensory-substitution devices to support perceptual judgments of affordances involving the task of passing through apertures. Sighted participants made perceptual judgments about whether they could walk through apertures of various widths and their level of confidence in each judgment, using unrestricted vision and, when blindfolded, using two haptic sensory-substitution instruments: a cane-like wooden rod and the Enactive Torch, a device that converts distance information into vibrotactile stimuli. The boundary between aperture widths that were judged as pass-through-able versus non-pass-through-able was statistically equivalent across sensory modalities. However, participants were not as confident in their judgments using the rod or Enactive Torch as they were using vision. Additionally, participants’ judgments with the haptic instruments were significantly more accurate than with vision. The results underscore the need to assess sensory-substitution devices in the context of functional behaviors.     

The Limits of Attention for Visual Perception and Action in Aging

ABSTRACT

This study aimed to investigate whether aging results in an increased attentional blink effect in older adults as compared to young adults. A rapid serial visual presentation (RSVP) paradigm was employed in which participants were asked to identify two targets (dual-task condition) presented in rapid succession. These targets were separated by various intervals in a stream of stimuli. The performance for identifying the second target was normally diminished as compared to identification of a single-task target. Various combinations of tasks, such as two perceptual tasks or one perceptual and one action task, as well as different types of pointing action, such as pointing to a displaced target, pointing to a stationary target or pointing to a disappeared target, were manipulated in this study to see if aging may further impact these variables. The results of this study showed that in young adults, successful identification of the first target interfered with identifying the second target, as well as the initiation time (action planning) of pointing to the second target. However, identification of the first target did not interfere with pointing movement time and pointing accuracy, even when the target was displaced, which required online control of action. Conversely, for older adults, successful central identification not only interfered with identifying the second target and with the pointing initiation time, but also interfered with pointing movement time for a displaced target. This suggests that older adults seem to be unable to concurrently identify the first target and correct their already-initiated pointing movement compared to young adults.     

Children's working understanding of the knowledge gained from seeing and feeling

In three experiments (N = 48 3‐ to 4‐year olds; 100 3‐ to 5‐year olds; 54 4‐year‐olds), children who could see or feel a target toy, recognized when they had sufficient information to answer ‘Which one is it?’ and when they needed additional access. They were weaker at taking the informative modality of access when the choice was between seeing more of a partially visible toy and feeling it; at doing so when the target was completely hidden; and at reporting seeing or feeling as their source of knowledge of the target's identity having experienced both. Working understanding of the knowledge gained from seeing and feeling (identifying the target efficiently) was not necessarily in advance of explicit understanding (reporting the informative source).     

Children's understanding of teaching: the role of knowledge and belief

The relation between preschoolers’ concept of teaching and theory of mind was explored to determine if there is a developmental change in understanding how teaching depends on knowledge and belief. The study tested whether 3- to 6-year-olds thought the awareness of a knowledge difference is necessary for teaching. The 3- and 4-year-olds understood teaching stories with clear knowledge differences and could correctly use that information to specify the teacher and learner. The 5- and 6-year-olds, who performed well on a standard false belief task, further understood that it was the teacher's belief about the knowledge difference that would actually govern teaching. The conceptual link to teaching suggests that theory of mind is critical for understanding other forms of knowledge acquisition besides perceptual access.     

Catching and matching bars with different orientations

The hypothesis that perception enslaves action is examined by assessing whether systematic distortions in perceptual judgments are reflected by inaccuracies in catching. In the first experiment, participants had to align manually the orientation of a reference bar placed at different distances in the frontoparallel plane. In the second experiment participants had to catch differently orientated moving bars, which became invisible at different distances from the interception point. In the matching experiment, systematic errors in the alignment of orientation were found in particular for oblique orientations, the magnitude of which increased with increasing distance of the reference bar. The inaccuracies in the final hand orientation during the catching task, however, did not mirror this pattern of deviations. The findings are interpreted to be more consistent with recent views that vision for perception (i.e., matching) and vision for action (i.e., catching) are dissociated than with the view that perception enslaves action.     

A common perceptual parameter for stair climbing for children,young and old adults

In this paper we examine whether a common perceptual parameter is available for guiding old adults, young adults and children in climbing the highest stair mountable in a bipedal fashion. Previous works have shown that the ratio between the height of the stair and the hip height was the body-scaled invariance adopted as information for selecting the highest stair by young adults [Journal of Experimental Psychology: Human Perception and Performance 10 (1984) 683-703] but not by older adults [Journal of Experimental Psychology: Human Perception and Performance 3 (1992) 691-697]. Indeed, for older adults additional bio-mechanical parameters needed to be added to the model due to their decrease in leg strength and flexibility.Up to now, no perceptual invariant has been identified yet for determining the relevant information used for guiding the stair climbing action for normal healthy people. We propose a new parameter as the angle defined by the ratio between the height of the stair and the distance taken from the feet to the top edge of the stair before the initiation of the movement. We show that this angle is the same for children, young adults and older adults despite the different kinematics of the motion, the anthropometrics and the skill ability exhibit by the participants. In summary we show that even when the climbability judgments, based on the simple ratio leg length-stair height, are influenced by differences in age, participants use a common perceptual variable when they are coordinating their stair climbing action.     

Infants' understanding of occlusion of others' line-of-sight: Implications for an emerging theory of mind

Infants' gaze following provides information about their understanding of others' perception and attention. Gaze following when the other looks in the presence (and absence) of visual obstacles can be especially informative. In the present study the gaze-following behaviour of 14- and 18-month-old infants was examined in opaque barrier, clear barrier, and non-barrier situations in order to investigate whether infants at this age understand the referential nature of looking. A hypothesis positing that infants grasp the referential nature of gaze would predict that infants would not follow gaze when the looker's gaze is blocked (as in an opaque barrier situation), but would follow gaze in both non-barrier and clear barrier situations. This hypothesis was contrasted with two other “leaner” interpretations predicting contrasting patterns of looking in the same situations. Results showed that both 18- and 14-month-old infants followed gaze as predicted by the richer, referential account.     

Functional dissociation between perception and action is evident early in life

The functional distinction between vision for perception and vision for action is well documented in the mature visual system. Ganel and colleagues recently provided direct evidence for this dissociation, showing that while visual processing for perception follows Weber's fundamental law of psychophysics, action violates this law. We tracked the developmental trajectory of this functional dissociation, asking whether the qualitatively different pattern observed in adults of adherence of perception but not of action to Weber's law would also be evident early in life. Children aged 5-8 and adults were asked to either estimate the size of discs (perception) or grasp discs (action) varying in diameter. Interestingly, variability of perceptual estimates increased as a function of object size in accord with Weber's law, while variability of grasping did not scale with object size, at all ages tested. This provides the first clear evidence for an early emergence of the dissociation between perception and action.     

Listening in aging adults: from discourse comprehension to psychoacoustics.

Older adults, whether or not they have clinically significant hearing loss, have more trouble than their younger counterparts understanding speech in everyday life. These age-related difficulties in speech understanding may be attributed to changes in higher-level cognitive processes such as language comprehension, memory, attention, and cognitive slowing, or to lower-level sensory and perceptual processes. A complicating factor in determining how these sources might contribute to age-related declines in speech understanding is that they are highly correlated. Experimenters have typically focused either on cognitive declines or sensory declines in artificially optimized test conditions. In contrast, our approach focuses on the complex interactions between age-related changes in cognitive and perceptual factors that affect spoken language comprehension, especially in nonideal, realistic conditions. In this article, we describe our attempts to systematically investigate sensory-cognitive interactions in controlled experimental situations. We begin by looking at experimental conditions that closely approximate everyday listening, and show that older adults do indeed experience deficits in spoken language comprehension relative to younger adults in these conditions. We then review further experiments designed to isolate more precisely the cognitive and perceptual sources of these age-related differences and how they vary with listening condition. In large part, we find that age-related changes in speech understanding are a consequence of auditory declines.     

Action control: independent effects of memory and monocular viewing on reaching accuracy

Evidence suggests that perceptual networks in the ventral visual pathway are necessary for action control when targets are viewed with only one eye, or when the target must be stored in memory. We tested whether memory-linked (i.e., open-loop versus memory-guided actions) and monocular-linked effects (i.e., binocular versus monocular actions) on action arise from a common mechanism as suggested by evidence from neuropsychology and psychophysics. Participants viewed targets with either one eye or two (vision: monocular versus binocular) and then reached to touch targets in open-loop and memory-guided conditions (condition: open-loop versus 0, 500, 1000, and 1500 ms delays). Results showed that memory-linked and monocular-linked increases in radial and variable movement error were additive (i.e., main effects of vision and condition, but no interaction). This suggests that the two effects on visuomotor control arise from separate mechanisms, in contrast to evidence from psychophysics and neuropsychology suggesting a common underlying mechanism.     

Retracing Augustine's Ethics

Augustine's exposition of the image of God in Book 15 of On The Trinity (De Trinitate) sheds light on multiple issues that arise in scholarly interpretations of Augustine's account of lying. This essay argues against interpretations that posit a uniform account of lying in Augustine—with the same constitutive features, and insisting both that it is never necessary to tell a lie and that lying is absolutely prohibited. Such interpretations regularly employ intertextual reading strategies that elide distinctions and developments in Augustine's ethics of lying. Instead, I show how looking at texts written prior and subsequent to the texts usually consulted suggests a trajectory in Augustine's thought, beginning with an understanding of lies as morally culpable but potentially necessary, and culminating in a vision of lying as the fundamental evil and the origin of every sin.     

Perception of visual inclination in a real and simulated urban environment

The perceived inclination of slopes is generally overestimated. We claim that overestimation depends on the use of impoverished stimuli and on the distance between the observer and an inclined surface. In experiment 1, participants reported the perceived inclination of a set of urban roads from two different viewing distances. Observers did not overestimate the perceived inclination of slopes when they saw roads from the shorter viewing distances, whereas they slightly overestimated the perceived inclination of slopes from the farther distance. In experiment 2, participants reported the perceived inclination of a set of stereoscopic slides representing the same urban roads as in experiment 1. Here, observers did not overestimate the perceived inclination of slopes when the projected stereoscopic image contained horizontal disparity and simulated the shorter viewing distance; while they revealed a slight overestimation from the farther distance. We found always overestimation when the binocular image did not contain horizontal disparity, independently from the viewing distance. In conclusion, slopes are overestimated when (a) horizontal disparity is absent, and (b) the viewing distance is increased.     

Gut estimates: Pregnant women adapt to changing possibilities for squeezing through doorways

Possibilities for action depend on the fit between the body and the environment. Perceiving what actions are possible is challenging, because the body and the environment are always changing. How do people adapt to changes in body size and compression? In Experiment 1, we tested pregnant women monthly over the course of pregnancy to determine whether they adapted to changing possibilities for squeezing through doorways. As women gained belly girth and weight, previously passable doorways were no longer passable, but women’s decisions to attempt passage tracked their changing abilities. Moreover, their accuracy was equivalent to that of nonpregnant adults. In Experiment 2, nonpregnant adults wore a “pregnancy pack” that instantly increased the size of their bellies, and they judged whether doorways were passable. Accuracy in the “pregnant” participants was only marginally worse than that of actual pregnant women, suggesting that participants adapted to the prosthesis during the test session. In Experiment 3, participants wore the pregnancy pack and gauged passability before and after attempting passage. The judgments were grossly inaccurate prior to receiving feedback. These findings indicate that experience facilitates perceptual–motor recalibration for certain types of actions.